PORTLAND, Ore.  A massive census of all the fish and other marine life in the world's oceans has reached the halfway point with new evidence of the rich diversity under the sea along with warnings about the alarming decline of many species.

The 10-year international project that began in 2000 already has tracked the migration of tuna from Japan to California and back, along with the movement of endangered British Columbia salmon with implanted computer chips.

"We're sending animals out with the equivalent of cell phones and they're telling us where they are," said Ron O'Dor, senior scientist for the Census of Marine Life.

"What those animals are sending back is a picture that shows what seems like a blue uniform ocean to us on the surface is really very complicated," O'Dor said.

The data from the tracking program could help researchers and fishery managers conserve stocks of many species of large fish that have declined by about 90 percent over the last 50 years, O'Dor said.

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"This gives us an idea about where fish go, the rate at which they migrate, and tells us where these animals live and where they die so we can understand quantitatively what happens to fish stocks so we can manage them better," he said.

Dave Fluharty, a marine policy analyst at the University of Washington, said the data likely will change international treaties on fishing rights as researchers find out how fish are distributed in the ocean.

"It's going to be easier to detect international violations, and I think that's going to change a lot of what we do over the next 10 to 20 years," Fluharty said.

Jane Lubchenco, an Oregon State University marine biologist and president of the International Council for Science, said the census will help raise awareness about the urgent need for international cooperation to preserve marine life.

"I think there's definitely increasing recognition that we can no longer think about the ocean as infinitely vast, infinitely bountiful and infinitely resilient," Lubchenco said. "There are problems everywhere."

But she said she was encouraged by the amount of biological diversity the census has found in the first five years.

"The expectation was there would be new discoveries," Lubchenco said. "What's blown us away is how much there is out there that we didn't know about before. It's big stuff, it's little tiny stuff that's been coming in from this project. It's been pretty sobering."

Other highlights at the midway point of the census include the discovery of tiny carnivorous sponges found in the Southern Ocean abyss, an underwater dead zone at the epicenter of the 2004 tsunami and the first life recorded at smoking seafloor vents south of the equator in the Atlantic.

The census also is studying polar regions and the deepest reaches of the oceans. Scientists recently used the German icebreaker Polarstern to tow an underwater sled over the Southern Ocean floor near Antarctica to photograph life at the bottom.

"The old way was to drop a bucket and maybe collect one sea cucumber," O'Dor said. "But when you tow the photo sled you could see the sea cucumbers for miles and miles across the bottom."

But O'Dor noted the cost of such research is very expensive, estimated at more than a dollar per second to operate the Polarstern.

As a result, many scientists in the census are turning to private industry to share ocean data, including the oil industry.

Drilling crews are moving farther out along the continental shelves across the world, and much of the information they obtained was simply filed away and forgotten once the right site was found. But that data is a gold mine for researchers, O'Dor said.

"This is billions of dollars worth of sampling because the oil companies have more equipment and ship time than all the scientists in the world," O'Dor said. "If we can work with them it gives us a way of making progress."